Mercury and its compounds are significant environmental pollutants and major threats to human life and natural ecosystems. Mercury is of significant environmental concern because of its toxicity, persistence in the environment, and bioaccumulation in the food chain. The toxicity of soluble Hg ions and elemental Hg even in very dilute concentrations has been widely reported in the literature. Mercury is released readily into the environment from natural and anthropogenic sources. Because of its physical and chemical properties, mercury can also be transported regionally through various environmental cycles. Mercury Study Report to Congress, “Volume VIII: An Evaluation of Mercury Control Technologies and Costs,” U.S. Environmental Protection Agency, EPA452/R-97-010, December, 1997.1 Atmospheric deposition of mercury is reported to be the primary cause of elevated mercury levels in fish which is a potential threat to pregnant women and young children. 2004 EPA and FDA Advice, “What You Need to Know About Mercury in Fish and Shellfish,” EPA-823-R-04-005, March, 2004.2 
The annual global mercury emission is estimated at 5000 tons. Miller, S. J., et al., “Laboratory-Scale Investigation of Oxidative sorbents for Mercury Control,” 94-RA 114A.01, presented at the 87th Annual Air and Waste Management Meeting, Cincinnati, Ohio, Jun. 19-24, 1994.3 
The United States accounts for approximately 3% of such mercury emissions although this persistent pollutant travels globally via jet stream and gets converted to methyl mercury in the environment with high neurodevelopment toxicity. In the United States, coal-fired power utility plants are the biggest source of mercury emissions into the air, emitting a total of about fifty metric tons of mercury into the atmosphere annually, which is approximately thirty-three percent of all mercury emissions from the United States. Coal-fired combustion flue gas streams are of particular concern because of their composition that includes trace amounts of acid gases, such as SO2, NOx, and HCl plus CO2 and oxygen contents. Other sources of mercury emissions may include the chlor-alkali industry, metal sulfide or smelting, gold refining, cement production, fossil fuel combustion and incineration of sewage sludge or municipal garbage or the like.
The major chemical forms of the metal in the combustion flue gases are the elemental Hg0 (zerovalent) and the oxidized mercury, HgCl2, Hg(I) and Hg(II). Mercury vapor, Hg0, is found predominantly in coal-fired boiler flue gas. Mercury can also be bound to fly ash in the flue gas. Mercury speciation (elemental or oxidized) and concentration is dependent on the source (e.g. the characteristics of the fuel being burned), process conditions and the constituents in the ensuing gas streams (e.g., Cl2, HCl, SO2, NOx). The thermodynamically stable predominant form of mercury in the flue gases from coal-fired utilities is the elemental one (Hg0). However, the oxidized HgCl2 may be the major species from waste incinerators. Unlike the oxidized forms, the metal in the zero valent state is difficult to remove due its high volatility and low water solubility.
There is no currently available control method that efficiently collects all mercury species present in the flue gas stream. The existing mercury removal technologies involve scrubbing solution as in a wet flue gas desulfurization system, filtration and other inertial methods, electrostatic precipitation, and activated carbon based sorbents and a few other types of sorbents. For example, phyllosilicate mineral based sorbent has been described using a polyvalent metal sulfide prepared by ion exchange of tin, iron, titanium, zirconium and molybdenum to the support, and sequentially controlled addition of sulfide ions to the silicate substrate. However, the preparation and regeneration is tedious, costly, and dangerous making this technology unlikely to be commercialized.
Sorbent injection is one of the most promising technologies for application to the utility industry as virtually all coal-fired boilers are equipped with either an electrostatic precipitator (ESP) or a baghouse. Among various sorbents tested under the Department of Energy (DOE)'s field testing program, the most widely tested and promising sorbent is found to be activated carbon which has displayed the capability of capturing both elemental and oxidized mercury from flue gas streams. However, activated carbon has the following limitations: (1) activated carbon is expensive (e.g., Norit DARCO FGD activated carbon, DOE's benchmark sorbent, costs $0.42/lb); (2) it requires a very high carbon-to-mercury mass ratio (3,000-100,000) especially in flue gases with low HCl content such as subbituminous and lignite coals, and cannot achieve 90%+mercury removal. Mercury Study Report to Congress; EPA 452/R-97-003; U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards: Washington, D.C., December 1997.4; and (3) it degrades the quality of captured fly ash and thereby adversely impacts its sale as a pozzolan additive. Feeley, T. J.; Brickett, L. A.; O'Palko, B. A.; Murphy, J. T. Field Testing of Mercury Control Technologies for Coal-Fired Power Plants. Procd. of DOE/NETL's Mercury Control Technology R&D Program Review Meeting, Pittsburgh, Pa., Jul. 12-14, 2005.5 
Accordingly, there has been a need for novel oxidative sorbent compositions and methods to substantially reduce mercury emissions into the environment. There has been a need for novel oxidative sorbent compositions and method which efficiently and economically substantially reduce mercury in mercury containing fluids such as vapor mercury, the elemental form of mercury, from flue gas while preserving the quality of fly ash. Such oxidative sorbents and methods are needed to substantially reduce the total cost of mercury control technology. Additionally, novel compositions and methods are needed to reduce the amount of oxidative sorbent and oxidative sorbent injection equipment needed, and reduce costs for handling and disposing of spent oxidative sorbent. There is a still further need for efficient oxidative sorbent compositions that exhibit high adsorption capacity and can tolerate the presence of acidic gases. There is an additional need for novel oxidative sorbent compositions and methods that are less expensive and more efficient than activated carbon alone at removing vapor mercury from flue gas and may be used in combination with other mercury-removal technologies. The present invention fulfills these needs and provides other related advantages.